The measurement of parts-per-trillion level acidic and basic airborne molecular contamination (AMC) is essential for process protection and yield control in semiconductor photolithography and adjacent applications. Real-time monitoring solutions are highly desired, as they provide instantaneous and continuous measurement. However, even the most advanced monitors cannot achieve detection limits in the low parts-per-trillion range, and many restrictions apply for the detection of acidic AMC.
Discontinuous sampling with sample traps is capable of achieving parts-per-trillion level measurement, but the currently accepted methods use sample traps filled with deionized water (also commonly referred to as impingers, bubblers and beakers, and all of which are referred to herein as impingers) to capture soluble acidic and basic AMC. Several inherent disadvantages of these methods result in inconsistent data and increased detection limits. Some proprietary solid state solutions have been reported, but involve complex preparation, have high background signals and require 24-72 hour sample duration, or they are protected trade secrets that are not available as an industry standard.
Thus, there is a need for a sample trap and analytical method for measuring trace level acidic and basic airborne molecular contaminants, particularly those acidic and basic airborne molecular contaminants typically encountered in the semiconductor industry, that overcomes these disadvantages, has a low (e.g., parts-per-quadrillion) detection limit and requires a shorter (e.g., 4-8 hour) sample time.